Table 1. Selected Covariates of Patients With Standardized Differences Before and After Inverse Probability of Treatment Weighting.
| Variable | Entire cohort | Short interval, ≤8 wk | Intermediate interval, >8 to ≤12 wk | Long interval, >12 wk | Standardized differencesa | |
|---|---|---|---|---|---|---|
| Before IPTW | After IPTW | |||||
| Center, No. (%) | ||||||
| Hospital Clínic de Barcelona | 271 (17.9) | 84 (16.4) | 133 (16.6) | 54 (27.2) | 0.8636 | 0.0680 |
| Hospital Clínico Universitario de Santiago | 538 (35.7) | 101 (19.7) | 404 (50.6) | 33 (16.6) | ||
| Hospital del Mar | 201 (13.3) | 73 (14.2) | 109 (13.6) | 19 (9.6) | ||
| Hospital Universitari Son Espases | 214 (14.2) | 122 (23.8) | 88 (11) | 4 (2) | ||
| Consorci Sanitari Integral–Hospital General de Hospitalet | 163 (10.8) | 120 (23.4) | 36 (4.5) | 7 (3.5) | ||
| Hospital Clínico Universitario Virgen de la Arrixaca | 119 (7.9) | 11 (2.1) | 27 (3.3) | 81 (40.9) | ||
| Age, median (IQR), y | 68.8 (59.4-76.5) | 68 (59-77) | 69 (60-77) | 66.6 (59-76) | 0.0145 | 0.0377 |
| Sex, No. (%) | ||||||
| Male | 908 (60.3) | 293 (57) | 492 (61.7) | 123 (62.1) | 0.0896 | 0.0261 |
| Female | 598 (39.7) | 218 (42.7) | 305 (38.3) | 75 (37.9) | ||
| BMI, No. (%)b | ||||||
| <20 | 56 (3.7) | 11 (2.2) | 34 (4.3) | 11 (5.6) | 0.1512 | 0.0228 |
| 20-24.9 | 383 (25.4) | 128 (25.1) | 196 (24.6) | 59 (29.8) | ||
| 25-30 | 615 (40.8) | 210 (41.1) | 329 (41.3) | 76 (38.4) | ||
| >30 | 284 (18.9) | 105 (20.6) | 136 (17.1) | 43 (21.7) | ||
| Missing | 168 (11.2) | 57 (11.2) | 102 (12.8) | 9 (4.6) | ||
| Smoker, No. (%) | ||||||
| No | 1245 (82.7) | 450 (88.1) | 660 (82.8) | 135 (68.2) | 0.1493 | 0.010 |
| Yes | 261 (17.3) | 61 (11.9) | 137 (17.2) | 63 (31.8) | ||
| Hypertension, No. (%) | ||||||
| No | 809 (53.7) | 274 (53.6) | 420 (52.7) | 115 (58.1) | 0.0185 | −0.001 |
| Yes | 697 (46.3) | 237 (46.4) | 377 (47.3) | 83 (41.9) | ||
| Diabetes, No. (%) | ||||||
| No | 1180 (78.4) | 406 (79.4) | 628 (78.8) | 146 (73.7) | 0.0162 | −0.017 |
| Yes | 326 (21.7) | 105 (20.6) | 169 (21.2) | 52 (26.3) | ||
| Chronic kidney disease, No. (%) | ||||||
| No | 1457 (96.7) | 494 (96.7) | 769 (96.5) | 194 (98) | 0.0162 | −0.017 |
| Yes | 49 (3.3) | 17 (3.3) | 28 (3.5) | 4 (2) | ||
| Chronic heart disease, No. (%) | ||||||
| No | 1279 (84.9) | 441 (86.3) | 678 (85.1) | 160 (80.8) | 0.0162 | −0.017 |
| Yes | 227 (15.1) | 70 (13.7) | 119 (14.9) | 38 (19.2) | ||
| Chronic obstructive pulmonary disease, No. (%) | ||||||
| No | 1365 (90.6) | 469 (91.8) | 716 (89.8) | 180 (90.9) | 0.0673 | 0.0246 |
| Yes | 141 (9.4) | 42 (8.2) | 81 (10.2) | 18 (9.1) | ||
| Chronic liver disease, No. (%) | ||||||
| No | 1474 (97.9) | 500 (97.9) | 782 (98.1) | 192 (97) | 0.0673 | 0.0246 |
| Yes | 32 (2.1) | 11 (2.1) | 15 (1.9) | 6 (3) | ||
| Vasculopathy, No. (%) | ||||||
| No | 1452 (96.4) | 493 (96.5) | 770 (96.6) | 189 (95.5) | −0.007 | 0.0178 |
| Yes | 54 (3.6) | 18 (3.5) | 27 (3.4) | 9 (4.5) | ||
| Previous malignancies, No. (%)c | ||||||
| No | 1429 (95) | 485 (95.1) | 766 (96.2) | 178 (89.9) | 0.0664 | 0.0653 |
| Hematologic | 7 (0.5) | 2 (0.4) | 4 (0.5) | 1 (0.5) | ||
| Colorectal | 5 (0.3) | 1 (0.2) | 1 (0.1) | 3 (1.5) | ||
| Otherd | 63 (4.2) | 22 (4.3) | 25 (3.1) | 16 (8) | ||
| ASA classification, No. (%) | ||||||
| I-II | 1029 (68.4) | 370 (72.7) | 524 (65.7) | 135 (68.2) | 0.1508 | −0.045 |
| III-IV | 475 (31.6) | 139 (27.3) | 273 (34.3) | 63 (31.8) | ||
| CEA, mean (SD), ng/mL | 8.99 (20.1) | 10.44 (27.8) | 8.24 (14.4) | 7.82 (11.4) | −0.10 | −0.083 |
| Height from AV, No. (%), cm | ||||||
| <5 | 480 (31.9) | 162 (31.7) | 244 (30.6) | 74 (37.4) | 0.0257 | 0.0368 |
| 5-10 | 774 (51.4) | 260 (50.9) | 415 (52.1) | 99 (50) | ||
| >10 | 252 (16.7) | 89 (17.4) | 138 (17.3) | 25 (12.6) | ||
| Clinical tumor (T) classification, No. (%) | ||||||
| cT1 | 9 (0.6) | 1 (0.2) | 4 (0.5) | 4 (2) | 0.1678 | 0.0797 |
| cT2 | 99 (6.7) | 26 (5.2) | 64 (8.2) | 9 (4.5) | ||
| cT3 | 1157 (76.5) | 404 (80.2) | 598 (74) | 155 (78.3) | ||
| cT4 | 241 (16.2) | 73 (14.5) | 138 (17.6) | 30 (15.2) | ||
| Clinical nodal (N) classification, No. (%) | ||||||
| cN0 | 372 (24.7) | 113 (22.1) | 184 (23.1) | 75 (37.9) | 0.0667 | 0.0438 |
| cN1 | 791 (52.5) | 272 (53.2) | 437 (54.8) | 82 (41.4) | ||
| cN2 | 312 (20.7) | 114 (22.3) | 162 (20.3) | 36 (18.2) | ||
| cNx | 31 (2.1) | 12 (2.4) | 14 (1.8) | 5 (2.5) | ||
| Baseline threatened CRM, No. (%) | ||||||
| No | 478 (31.7) | 189 (37) | 216 (27.1) | 73 (36.9) | 0.3834 | 0.0089 |
| Yes | 620 (41.2) | 223 (43.6) | 294 (36.9) | 103 (52) | ||
| Missing | 408 (27.1) | 99 (19.4) | 287 (36) | 22 (11.1) | ||
| Baseline EMVI, No. (%) | ||||||
| No | 860 (57.1) | 328 (64.2) | 396 (49.7) | 136 (68.7) | 0.4141 | 0.0192 |
| Yes | 257 (17.1) | 94 (18.4) | 120 (15.1) | 43 (21.7) | ||
| Missing | 389 (25.8) | 89 (17.4) | 281 (35.3) | 19 (9.6) | ||
| Clinical stage, No. (%) | ||||||
| I | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0.0257 | 0.0368 |
| II | 398 (26.4) | 122 (23.9) | 197 (24.7) | 79 (39.9) | ||
| III | 1108 (73.6) | 389 (76.1) | 600 (75.3) | 119 (60.1) | ||
| Radiotherapy, No. (%) | ||||||
| No | 0 (0) | 0 (0) | 0 (0) | 0 (0) | −0.004 | 0.0233 |
| Yes | 1506 (100) | 511 (100) | 797 (100) | 198 (100) | ||
| Chemotherapy, No. (%) | ||||||
| No | 177 (11.8) | 65 (12.7) | 98 (12.3) | 14 (7.1) | −0.004 | 0.0233 |
| Yes | 1329 (88.2) | 446 (87.3) | 699 (87.7) | 184 (92.9) | ||
| Type of chemotherapy, No. (%) | ||||||
| Capecitabine | 485 (36.1) | 151 (33.7) | 225 (31.6) | 109 (58.8) | −0.004 | 0.0233 |
| 5F | 844 (63.9) | 295 (66.3) | 474 (68.4) | 75 (41.2) | ||
| Type of radiotherapy, No. (%) | ||||||
| Short course | 177 (11.8) | 65 (12.7) | 98 (12.3) | 14 (7.1) | −0.012 | −0.035 |
| Long course | 1329 (88.2) | 446 (87.3) | 699 (87.7) | 184 (92.9) | ||
Abbreviations: ASA, American Society of Anesthesiologists; AV, anal verge; BMI, body mass index; CEA, carcinoembryonic antigen; CRM, circumferential resection margin; EMVI, extramural venous invasion; IPTW, inverse probability of treatment weighting.
SI conversion factor: To convert CEA to microgram per liter, multiply by 1.
a
Propensity score for IPTW calculation was performed by multinomial logistic regression model including all the variables shown in this table.
b
Calculated as weight in kilograms divided by height in meters squared.
c
Pelvic malignancy within the previous 5 years was an exclusion criterion.
d
Other malignancy includes skin cancer, breast cancer, and liver cancer.